Rotor structure for a turbomachine with features to control relative growth at axial interfaces

Abstract

Rotor structure for a turbomachine, such as a centrifugal compressor, is provided. Disclosed embodiments make use of structural and/or operational relationships (e.g., distinct axially-extending zones in the radially-inner contour of respective impeller bodies configured to balance mass distribution about a rotor axis) designed to control relative radial and/or axial growth between corresponding interface locations along the rotor axis at which corresponding faces of respective hirth couplings mesh with one another. The ability to control relative radial and/or axial growth between corresponding interface locations may be effective for reducing rotor vibration and/or to establish more reliable contact patterns and reduced levels of mechanical stresses and distortion (e.g., angular distortion) at the hirth coupling interfaces.

What is claimed is: 
     
       1. A rotor structure for a compressor, the rotor structure comprising:
 a tie bolt that extends along a rotor axis between a first end and a second end of the tie bolt; 
 a first rotor shaft fixed to the first end of the tie bolt; 
 a second rotor shaft fixed to the second end of the tie bolt; 
 a plurality of impeller bodies disposed between the rotor shafts, the plurality of impeller bodies supported by the tie bolt and mechanically coupled to one another along the rotor axis by way of a plurality of hirth couplings, wherein a radially-inner contour of an impeller body of the plurality of impeller bodies is characterized by at least two distinct axially-extending zones each having a respective geometry configured to balance mass distribution about the rotor axis and control relative radial and/or axial growth between corresponding interface locations along the rotor axis at which corresponding faces of a respective hirth coupling of the plurality of hirth couplings mesh with one another; 
 wherein the radially-inner contour of the impeller body comprises a first axially-extending zone, a second-axially-extending zone and an intermediate axially-extending zone, which is disposed between the first and second axially-extending zones, and 
 wherein the respective geometry of the intermediate zone is characterized by a varying bore diameter along the rotor axis, wherein a maximum of the varying bore diameter of intermediate zone is larger relative to the respective bore diameters of the first and second axially-extending zones. 
 
     
     
       2. The rotor structure of  claim 1 , wherein the respective geometry of the at least two axially-extending zones is characterized by a differing bore diameter size. 
     
     
       3. The rotor structure of  claim 1 , wherein the respective geometry of the at least two axially-extending zones is characterized by a differing axial length. 
     
     
       4. The rotor structure of  claim 1 , wherein the respective geometry of the at least two axially-extending zones is characterized by at least one of the following: a differing bore diameter size, and a differing axial length. 
     
     
       5. The rotor structure of  claim 1 , wherein the second axially-extending zone of the radially-inner contour of the impeller body is located axially downstream relative to the first axially-extending zone of the radially-inner contour of the impeller body and relative to an inlet eye of the impeller. 
     
     
       6. The rotor structure of  claim 5 , wherein mutually opposed axial sides of the first and second axially-extending zones of the radially-inner contour of the impeller body define respective notches configured to receive a radially-outward portion of the corresponding faces of the respective hirth coupling that mesh with one another. 
     
     
       7. The rotor structure of  claim 6 , wherein the respective notches defined by the mutually opposed axial sides of the first and second axially-extending zones of the radially-inner contour of the impeller body being subject to controlled relative radial and/or axial growth are effective to inhibit misalignment between the corresponding faces of the respective hirth coupling that mesh with one another. 
     
     
       8. The rotor structure of  claim 1 , wherein an axial side of the first axially-extending zone of the radially-inner contour of an impeller body proximate the first end of the tie bolt is mechanically coupled to the first rotor shaft by way of a further hirth coupling, wherein the axial side of the first axially-extending zone of the impeller body proximate the first end of the tie bolt and the corresponding axial face of the first rotor shaft define respective notches for supporting a radially-outward portion of the corresponding faces of the further hirth coupling that mesh with one another. 
     
     
       9. The rotor structure of  claim 8 , wherein the respective notches defined by the axial side of the first axially-extending zone of the impeller body proximate the first end of the tie bolt and the corresponding axial face of the first rotor shaft being subject to controlled relative radial and/or axial growth are effective to inhibit misalignment between the corresponding faces of the further hirth coupling. 
     
     
       10. The rotor structure of  claim 9 , wherein an axial side of the first axially-extending zone of the radially-inner contour of an impeller body proximate the second end of the tie bolt is mechanically coupled to the second rotor shaft by way of another hirth coupling, wherein the axial side of the first axially-extending zone of the impeller body proximate the second end of the tie bolt and the corresponding axial face of the second rotor shaft define respective notches for receiving a radially-outward portion of the corresponding faces of the another birth coupling that mesh with one another. 
     
     
       11. The rotor structure of  claim 10 , wherein the respective notches defined by the axial side of the first axially-extending zone of the impeller body proximate the second end of the tie bolt and the corresponding axial face of the second rotor shaft being subject to controlled relative radial and/or axial growth are effective to inhibit misalignment between the corresponding faces of the another birth coupling. 
     
     
       12. The rotor structure of  claim 1 , wherein a respective surface of revolution defined by a respective axially-extending zone of the first, second, and intermediate axially-extending zones is selected from the group consisting of a cylindrical surface of revolution, a conical surface of revolution, and a combination of two or more of a cylindrical surface of revolution and a conical surface of revolution. 
     
     
       13. A centrifugal compressor comprising the rotor structure of  claim 1 .